(a) Field
The present invention relates a method for controlling a power saving mode in a group communication.
(b) Description of the Related Art
A group communication service, in which users join in a conversation, simultaneously transmits the same downlink traffic to all the users of a group. Therefore, the group communication service can use a downlink multicast or broadcast connection as well as unicast connections. When the group communication service is used in a cellular-based wireless access system, a conventional broadcast service technology, for example a multicast broadcast service (MBS) technology or a terminal-based unicast service technology may be considered.
The conventional broadcast service supports a sleep mode for power saving of a terminal. In this case, entering or releasing the sleep mode is performed through unicast-based signaling, and a sleep cycle is controlled for each terminal.
If the conventional sleep mode is used in the group communication, unicast sleep mode signaling and unicast sleep mode control are performed for each terminal. However, when most terminals receive only the multicast-based group communication service, it is inefficient that sleep modes of the users within the group are controlled through the unicast signaling. Further, in order to quickly transit an idle mode to an active mode in the group communication, it is required to minimize a delay for transiting all the terminals within the group from a sleep state to an awake state or a normal state.
Therefore, when using the conventional sleep mode, it is required to set sleep cycles to be the same or to set listening windows to be close, for all sleep mode users within the group. However, these requirements make sleep cycles of terminals, which use other services as well as the group communication service, be restricted to the group communication service.